On Non-Standard Models of B\"uchi Arithmetics

B\"uchi arithmetics $\mathop{\mathbf{BA}}\nolimits_n$, $n\ge 2$, are extensions of Presburger arithmetic with an unary functional symbol $V_n(x)$ denoting the largest power of $n$ that divides $x$. We explore the structure of non-standard models of B\"uchi arithmetics and construct an example of a countable non-standard model of $\mathop{\mathbf{BA}}\nolimits_2$.